Furnace



March 21, 1939. L. DE FLoR'Ez 2,151,386

FURNACE v Filed April 16, 1929 2 sheets-shewb 2 Snowdon Patented Mar. 211939 FURNACE Luis de Flores, Pomfret, Conn., assignor to The TexasCompany, New York, N. Y., a corporation of Delaware Application April1e,

a4 claims.

My invention relates to furnaces, more particularly to tubular oilAheaters used in processes involving the heating' or cracking of oils,and has for its principal object the provision of a furnace of this typeby means of which a liquid such as oil can be thoroughly heated in aminimum of time,`the apparatus therefore taking up but a relativelysmall amount of space.

The use oi tubular oil heaters has developed rapidly in recent years,due to the fact that adequate turbulence can' be attained in these'tubesby high velocity and that the surface can be disposed at will to permitcomparatively even distribution of heat. In tubular heaters, especiallywhere economizers are used which consist of tubes placed across the uetobe heated Iby the outp flowing gases, it has been difficult to maintainthe gases at a velocity which will insure sufficient draft through theheater. One of the features of my invention lies in the construction ofan econo- 1 mizer, wherein provision is made for increasing the velocityof the gases as they pass through the flue.

In carrying out my invention in one form, with the above objects inview, I have provided a tubular oil heater which comprises what may betermed a main radiant section, a secondary radiant section, and aneconomizer section. The -main radiant section is constructed in the formof a vertical cylindrical shell, the walls of which are lined withvertically disposed tubes. Fuel is admitted to a burner located at oneend of the vertical chamber and the products oi.' combustion aredischarged atthe other end and carried to the economzer section througha horizontal flue. In this horizontal flue is arranged a second unit of'tubes positioned so as to be subjected tothe hot gases or products ofcombustion passing to the economizer. .'I'his last mentioned unit may betermed a secondary radiant heater. The economizer consists of a seriesof horizontal tubes arranged at right angles to the path of the gases. Aplurality of horseshoe-shaped strips are hung over certain of the tubesin a manner to 4.3 reduce the size of the passage progressively towardthe upper tubes whereby the velocity of the gases is increased as thegases pass through the economizer.

My invention will be better understood from the following descriptiontaken in -connection with the accompanying drawings and its scope willbe pointed out in the appended claims.

In the drawings Fig. 1 is a side elevation in section through a furnaceembodying my invention;

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Fig. 2 is a sectional elevation through the econo- 1929, serial No.atasco (ci. 19o-11o) mizer and secondary radiant section, and Fig. 3 isan enlarged -section through somje of the economizer tubes.

Referring to the drawings, I have illustrated a furnace comprising amain radiant heating section 5 I Il, a secondary radiant heating sectionI I and an economizer I2. A metallic wall or shell I3, preferablycylindrical in shape, defines the main heating chamber I4, the sides ofthis chamber being lined with suitable heat insulating, refractory l0material i5. The wall or shell I3 is supported by a suitable frameworkI6 resting on bases Il. An arch I9 of 'heat insulating material forms amajor part of the upper wall of the chamber I4, this arch beingsupported by suitable radial meml5 bers Isa from the framework I5.Located upon the arch I9 and directly over the center of the cylindricalchamber I4 is a. burner 20, and suitable inlets 2| and 22 may beprovided respectively for the gas and oil, while a third inlet 23 allows20 the admission of compressed air to the burner. Since the particulartype or form of burner does not form part of my invention, I have shownthis dlagrammatically only. At the center of the lower portion of thechamber I4 and directly op- 25 posite. the burner 20 is an outlet iue28, leading downwardly and then horizontally to the4 lower part of theeconomizer I2. It will thus be observed that upon the admission of fueland air to the burner and ignition thereof, a flame will be 30 producedand directed downwardly through the center-of the chamber I4, the hotgases of combustion therefrom passing into the fiue 2t.

In order to use to the fullest extent the radiant heat produced by theame in chamber I4, I have provided a plurality of tubes 25 arrangedvertically in a pair of concentric circles around the periphery of theheating chamber I 4. The tubes 25' are preferably supported or suspendedfrom their upper extremities from a flat annular tube sheet 26, thistube sheet 26 resting at its inner edge upon the arch I9 and at itsouter edge upon the refractory lining I5, thus forming the remainingpart of the top wall of the chamber I4. The upper and lower ends ofadjacent tubes 25 are connected together by means of return bends 28 ina manner such that a continuous path for liquid to be heated is formedthrough the tubes. In other words, the liquid to be heated enters one ofthe tubes 25 through an inlet pipe 29 50 and then passes from tube totube around the chamber I4, finally leaving the Atubes through an outlet30. While I have illustrated and described the tubes as being connectedin series, it is to be understood that they may be connected in parallelbe connected between one pair of headers so that the liquid will passthrough them al1 in the same direction at the same time, or small groupsof the tubes may be connected in parallel and these groups connected inseries.

Annular discs of heat insulating material 3i form part of the lower wallof the chamber I4 and serve to hold the tubes 25 in proper spacedrelation. An annular cover member 38 rests upon the framework supportingthe arch I9 directly above the tubes 25, and by removing this covermember access may be had to the tubes 25 for cleaning purposes or forremoval and .replacement of the tubes. That-portion of the furnacedescribed up to`this point is substantially the same as described in myco-pending application, Serial. Number 120,067, filed July 2, 19261, nowU. S. Patent 1,717,334, issued July 11, 1929.

The horizontal part of the outlet flue 24 is preferably circular insection and is lined with a layer of suitable heat insulatingmaterialll. 'I'he outer end of the horizontal flue 24 opens upwardlyinto the economizer I2. In the lower half of the flue 24 is arranged aplurality of tubes 38 extending horizontally and arranged preferably inthe form of a semi-circle as is shown more clearly in Fig. 2. 'I'hesetubes 38 are interconnected at their ends, thus forming a continuouspassage for the liquid entering one of the tubes from the economizer. Inthe arrangement illustrated, the liquid having been preheated in theeconomizer, passes through the tubes 38 in the flue 24, then through thepipe 29 to the tubes 25 in the main radiant heating section and iinallyout of the heater through the pipe 30. The tubes 38 will thus be heatedby the hot gases passing through the flue both by radiation and bypartial convective contact. The horizontal unit of tubes may thus betermed a secondary radiant heating section.

A plurality of tubes 39 are supported horizontally in the heatingchamber of the economizer and liquid entering these tubes through aninlet 40 passes downwardly through the tubes to an l outlet 4I theliquid in the passage thus absorbing heat from the hot gases passingupwardly through the economizer around the tubes. A flue 42 at the topof the economizer preferably leads to a stack (not shown) and a pair ofdampers 43 in this flue are adapted to control the draft through theeconomizer. A door 44 at each end of the horizontal flue 24 providesaccess to the interior.

In order to increase the velocity of the hot gases passing upwardlythrough the economizer I2, I have provided a plurality of metallicstrips 45, each strip being bent into the shape of a horseshoe or hairpin. 'I'hese strips`45 are hung upon and depend from the tubes 39 andare thus directly in the path of the hot gases. The nurnber of stripsincreases progressively toward the top of the economizer, as will beobserved withreference to Fig. 2 and hence it will be evident that thespace through which the hot gases pass in traveling through theeconomizer decreases in inverse proportion to the increase in number ofthe strips 45. The velocity-of these gases will thus be increased as thegases flow upwardly through the economizer. Since the strips 45 are ofmetal, they aid considerably in transferring or in series parallel; i.e., all of the tubes may mizer I2 and the inlet of the vertical tubes25. 'I'he bent strips 45 provide a simple and effective means forincreasing the velocity oi' the flue gases in the economizer and thusmaterially increase the efficiency of the furnace. A

While I have described my invention as embodied in concrete form inaccordance with the provisions oi' the patent statutes it should beunderstood that I do not limit my invention Y thereto, since variouschanges and modifications may be made without departing from the'scopeof the invention as defined by the accompanying`r in another of saidzones disposed substantially entirely below the point-oi' generation ofsaid` hot gases and the point of entry and withdrawal of said gasespassing therethrough, exposing substantially all of said fluid in saidother zone to radiant heat derived directly from said gases and heatingsaid fluid preponderantly by radiation.

2. 'Ihe method o-f heating hydrocarbon uid to elevated temperature,which comprises generating hot combustion gases, flowing hot combustiongases through a furnace, in an upper zone of said furnace applying heatderived from said gases to the petroleum by convection, and in anotherzoneof said furnace,.below the firstnamed zone and below the point ofgeneration of said gases and the point of entry and withdrawal of saidgasespassing through said other zone, exposing substantially all of saidpetroleum in said other zone to radiant heatderived directly from saidgases and heating said petroleum preponderantly by radiation and therebylimiting the temperature rise of the petroleum'in said first-named zone.4

3. 'I'he method of heating hydrocarbon fluid to elevatedtemperaturawhichcomprises generating hot products of combustion, flowing said hotproducts of combustion through different heating zones, passing a streamof hydrocarbon fluid through one of said zones and therein applying heatderived from said gases flowing therethrough to said stream byconvection, passing said stream through another of said heating zones ina path substantially entirely below the point of generation of said hotproducts of combustion and the point of entry and withdrawal of said hotproducts of combustion flowing throughsaid other zone, and exposingsubstantially all of said fluid in said other zone to radiant heatderived directly from said hot products of combustion and heating saidfluid preponderantly by radiation.

4. The method of heating hydrocarbon fluid to elevated temperature,which comprises generating hot'prcducts of combustion in a separatecombustion zone wherein at least partial combustion takes place, flowingsaid hot products of combustion through different heating zones, passinga stream of hydrocarbon fluid through one of said zones and thereinapplying heat derived from said gases flowing therethrough to saidstream by convection, passing said stream through another of saidheating zones in a path substantially entirely below `the point ofgeneration of said hot products of comaromas bustion and the point ofentry and withdrawal of said hot products of combustion iiowing throughsaid other zone, and exposing substantially all of said iiuid insaidother zone to radiant heat derived directly from said hot products ofcombustion and heating said fluid preponderantly by radiation.

y5. Oil heating apparatus ior heating oil to conversion temperaturecomprising separate heat-absorption structures for conveying oil beingheated disposed in dierent zones, means for producing a current of hotcombustion gases throughsaid zones in series and for heating theabsorption structure in one 4oi? said zones by convection, theheat-absorption structure of another of said zonesdisposed-substantially entirely below said means for producing said hotgases andthe point oi entry and withdrawal of gases with substantiallyall of sali second-mentioned heat-absorption structure being exposeddirectly to radiation from said gases and heated preponderantly byradiation.

6. Oil heating apparatus for heating oil to conversion temperaturecomprising separate heat-absorption'structures disposed in different'zones, means for producing a current of hot combustion gases `throughsaid zones in series and for heating the absorption structure in one ofsaid zones by convection, the heat-absorption structure of another ofsaid zones horizontally disposed substantially entirely below said meansfor producing said hot gases and the point of entry of gases therein andsubstantially entirely below the point of withdrawal of gases therefrom,with substantially all of said last-mentioned heatabsorption structurebeing exposed directly to radiation from said gases and heatedpreponderantly by radiation, and means for conducting the 'oil from theheat-absorption structure in one of said zonesto theheat-absorptionstructure in the other of said zones.

7. Oil heating apparatus for heating oil to conversion temperaturecomprising a heating chamber, means for introducing combustion gasesinto said chamber to effect a current of hot gases through said chamber,said chamber arranged to cause said combustion gases to flow through asubstantial part thereof in a substantially rectilinear flow,heat-absorption structure in another chamber reoeiving said gases fromthe rst-mentioned chamber adapted to absorb heat by convection from saidgases, and means for reducing the temperature of said gases to preventexcessive temperature of said heat-absorption structure comprisingheat-absorption structure horizontally disposed in said first-mentionedchamber substantially entirely below said means for introducingcombustion gases and the point of entry and withdrawal of saidcombustion gases passing through said first-mentioned chamber withsubstantially all of said heat-absorption structure being exposeddirectly to radiation from said gases and absorbing heat preponderantlyby radiation, and means for connecting said heat-absorption structuresfor passage of the oil therethrough in succession.

8. Heating apparatus for heating hydrocarbon uid to conversiontemperature comprising a plurality of chambers, means for producing acurrent of hot gases through said chambers in succession, oil-conductingtubes disposed in one of said chambers to absorb heat from said gasespreponderantly by-convection, and oil-conducting tubes, connected tosaid first-named tubes,

lhorizontally disposed adjacent the bottom of I another ot said chamberssubstantially entirely below said means for producing said hut gases andthe pointof entry and withdrawal of the current of gases, withsubstantially all o! said second-mentioned oil conducting tubes beingexposed directly to radiation from said gases and heated preponderantlyby radiation.

9. Oil heating apparatus for heating oil to conversion temperaturecomprising separate heat-absorption structures disposed in dierentzones, means for producing a current oi' hot combustion gases forpassage through said Azones in series and for heating the absorptionstructure in one of said zones by convection, bare tubularheat-absorption structure, in another of said zones, horizontallydisposed below substantially the entire convectively heated absorptionstructure and said means for producing said hot gases and substantiallyentirely below the point of entry and withdrawal of combustion gasespassing through said last-mentioned chamber, with substantially all ofsaid last-mentioned heat-absorption structure being exposed directly toradiation from said gases and heated preponderantly by radiation, andmeans for connecting said absorption structures for passage oi' the oiltherethrough in succession.

10. Heating apparatus for heating hydrocarvbon fluid to conversiontemperature comprising by convection, another of said zones beingarranged to cause said hot combustion gases passing therethrough to flowthrough a substantial part thereof in a substantially rectilinear path,the heat-absorption structure of said last mentioned zone being disposedsubstantially horizontally and substantially entirely below said meansfor producing said hot gases and the point of entry and withdrawal ofgases passing through said last-mentionedl zone, with substantially al1of said second-mentioned heat-absorption structure being exposeddirectly to radiation from saig gases and heated preponderantly byradiatio 11. A furnace for heating hydrocarbon fluid to conversiontemperature comprising a heating chamber, means for producing hot gasesfor passage through said chamber, another heating chamber traversed bysaid hot gases, heat-absorption structure disposed in saidsecond-mentioned heating chamber to receive heat -from the gases byconvection, another heat-absorption structure disposed in saidfirst-mentioned heating chamber substantially entirely below said meansfor producing hot gases and the point of entry and withdrawal of saidhot gases passing through the first-mentioned heating chamber withsubstantially all of saidlast-mentioned structure being exposed toradiation from said gases and heated preponderantly by radiation, andmeans for connecting said heat-absorption structures for passage of thefluid to be heated.

l2. In a furnace for heating hydrocarbon uids to conversion temperature,a heating chamber. means for producing hot combustion gases for passagethrough said heating chamber, conduit elements for conveying hydrocarbonfluid being heated in said heating chamber disposed substantiallyentirely below said means and the point of entry and withdrawal of saidhot gases passing through said chamber, with substantially all of saidconduit elements being exposed directly .to radiation from said gasesand heated prcponderantly by radiation, and other conduit elements forconveying hydrocarbonfluid being directly exposed to said hot combustiongases and heated preponderantly by radiation.

13. In a furnace for heating hydrocarbon oils to conversion temperature,a radiant heating section, heat-absorbing tubes therein for conveyingoil to beheated, means for producing hot products of combustion to heatsaid tubes by radiant heat, another radiant heating section positionedbelow said combustion producing means and in communication with saidrstmentioned heating section for the passage of hot products ofcombustion, separate heat-absorbing tubes for conveying oil being heatedwithin said second-mentioned heating section horizontally disposedsubstantially entirely below the means for producing hot products ofcombustion and the point of entry and withdrawal of said products ofcombustion passing through said second-mentioned heating section, withat least a part of said tubes being adjacent the floor and withsubstantially all of them being exposed directly to radiation from saidproducts of combustion .and heated preponderantly by radiant heat, andmeans for connecting the heat-absorbing tubes in one section to those ofthe other heating section.

14. In a furnace for heating hydrocarbon oils to conversion temperature,a heating section, heat-absorbing tubes therein adapted to be heated byradiation,another heating section below.

said first-mentioned heating section, Ameans for producing hot productsof combustion for passage through said heating sections, separateheatabsorbing tubes in said second-mentioned heating sectionhorizontally disposed substantially entirelyl below said combustionproducing means and the point of entry and withdrawal of said hot gasespassing through the second-mentioned heating chamber, with at least apart of said tubes being adjacent the floor and with substantially allof them being exposed directly to radiation from said products ofcombustion and heated preponderantly by radiant heat, and means forconnecting the 'heat-absorbing tubes in one section to those of theother heating section.

' 15. In a furnace for heating hydrocarbon oils to conversiontemperature, a combustion chamber having means for producing hotproducts of combustion associated therewith, a heating chamber connectedto said combustion chamber for receiving hot products of combustiontherefrom for passage therethrough and conduit elements for conveyingoilbeing heated in said heating chamber disposed substantially entirelybelow said means for producing hot products of combustion and the pointof entry and withdrawal of hot -products of combustion passing throughsaid heating chamber with substantially -all of said conduit elementsbeing'exposed directly to radiation from said products of combustion andheated preponderantly by radiation.

16. A system for transferring heat to a hydrocarbon fluid passed throughheat-absorption structures to be heated therein to conversiontemperature, comprising a combustion chamber, means for producing hotgases associated with said combustion chamber, a heating chamber intowhich said combustion chamber discharges hot gases, another heatingchamber extending upwardly above the outlet of said combustion chamberand traversed by said hot gases, heattherethrough of the fluid to beheated.

17. `A system for transferring heat to a hydrocarbon fluid passedthrough heat-absorption structures to be heated therein to conversiontemperature, comprising a combustion chamber. means for producing` hotgases associated with said combustion' chamber, a heating chamber intowhich said combustion chamber discharges hot gases, another heating'chamber traversed by said hot gases, heat-absorption structure disposedwithin said second-mentioned chamber in the current of gases to receiveheat therefrom preponderantly by convection, a separate floor tubesection disposed in said mst-mentioned heating chamber substantiallyentirely below said means for producing said hot gases and the point ofentry and withdrawal of said hot gases passing through thefirst-mentioned heating chamber with substantially all of said floortube section being exposed directly to radiation from said gases andheated preponderantly by radiation, and means for connecting said iloortube section' and heat-absorption structure for passage therethrough ofthe fluid to be heated.

18. In a furnace for heating hydrocarbon oils to conversion temperature,a combustion chamber having means for producing hot products ofcombustion associated therewith, a heating chamber connected to saidcombustion chamber for receiving hot products of combustion therefromfor passage therethrough, conduit elements for conveying oil beingheated in said heating chamber and horizontally disposed substantiallyfirst-mentioned heating chamber to be heated preponderantly byconvection heat from, said hot products of combustion.

19. In a furnace for heating hydrocarbonbils to conversion temperature,a combustion chamber having means for producing hot products ofcombustion associated therewith, a heating chamber connected to saidcombustion chamber for receiving hot products of combustiontherefrom,said heating chamber arranged to cause said hot products of combustionto ow through a substantial part of said heating chamber in asubstantially rectilinear path, and horizontally disposed conduitelements for conveying oil being heated in said heating chamber arrangedin parallel relationship to each other and disposed subanimee stantiallyentirely below said means for producing said hot products of combustionand the point of entry and withdrawal of hot products of combustionpassing through said heating chamber with substantially all ot saidconduit elements being eixpos'ed directly `,to radiation from said gasesand heated preponderantly by radiation.

20. In a lfurnace for heating hydrocarbon oils to conversiontemperature, a combustion chamber having means for producing hotproducts of combustion associated therewith, a heating chamber connectedto said combustion chamber for receiving hot products of combustiontherefrom, said heating chamber arranged to cause said hot products olcombustion to ow through a substantial part of said heating chamber in asubstantially rectilinear path, conduit elements for conveying oil beingheated in said heating chamber and horizontally disposed substantiallyentirely below said means for producing said hot products of combustionand the y point of entry and Withdrawal of hot products of combustionpassing through said heating chamber with substantially all of saidconduit elements being exposed directly to radiation from said gases andheated preponderantly by radiation, another heating chamber connected tosaid first-mentioned heating chamber for receiving products ofcombustion therefrom, and conduit elements in said heating chamberconnected to said first-mentioned heating chamber to be heatedpreponderantly by convection heat from said hot products of combustion.

2l, A system for heating petroleum to conversion temperature comprisinga chamber arranged to cause combustion gases to ow through a substantialpart thereof in a substantially rectilinear iiow, a combustion chamberdischarging combustion gases into said chamber. means for producing hotgases associated with said combustion chamber, heat-absorbing structurein said first-named chamber horizontally disposed substantially entirelybelow said means for producing said hot gases and the point of entry anddischarge of gases passing through said firstmentioned chamber, withsubstantially all oi said heat-absorption structure being exposeddirectly to radiation fromk said gases and heated preponderantly byradiation, another heat-absorbing structure in said system to absorbheat by convection from said combustion gases, and connections forpassing the petroleum through said heat-absorbing structures insuccession.

22.,A system for transferring heat tofhydrocarbon fluid to raise saidfluid to conversion temperature comprising a chamber arranged to causecombustion gases to flow through a substantial part thereof in asubstantially rectilinear fiow, a `combustion chamber dischargingcombustion gases into said chamber, means for producing hotgasesassociated with said combustion chamber, heat-absorption structurehorizontally disposed in said first-named chamber comprising tubes, atleast somev of which are adjacent the discharge of said combustioncham'- ber and all of which are substantially entirely below said meansfor producing said Ahot gases and the point of entry and discharge ofsaid hot gases passing through said rst-mentioned chamber, withsubstantially all of said heatabsorption structure being exposeddirectly to radiation from said gases and heated preponderantly byradiation, heat-absorption structure in another zone of the systemadapted to absorb heat by convection from said combustion gases, andmeans for connecting said heat-absorption structures for passage of thefluid therethrough in succession.

23. A system for heating petroleum to conversion temperature, comprisinga housing structure enclosing a plurality of heating zones, a piuralityof heat-absorption structures disposed in different of said zones, meansfor connecting said absorption structures for passage of. the petroleumAtherethrough in succession,a combustion chamber discharging hotcombustion gases through said zones in succession, means for producinghot gases associated with said combustion chamber. a heat-absorptionstructure in one of said zones adapted to be heated by convection, andtubular heat-absorption structure in another of said zones, disposedsubstantially entirely below said means for producing said hot gases andthe point of entry and withdrawal of the stream of gases passing throughsaid other zone, with substantially all of said tubular heatabsorptionstructure being exposed directly to radiation from said gases and heatedpreponderantly by radiation.

24, Heat transfer apparatus for heating hydrocarbon fluid to conversiontemperature comprising means for producing combustion gases, a heatingchamber traversed by combustion gases, heat-absorption structure forconveying said fluid being heated disposed-in said chamber, anotherheating chamber traversed by combustion gases, other heat-absorptionstructure for conveying y said fluid being heated with at least a partthereof disposed adjacent the bottom of said lastmentioned chamber andwith all of it disposed substantially entirely below said means forproducing said combustion gases and the point of entry and withdrawal ofsaid combustion gases passing therethrough, with substantially all ofsaid heat-absorption structure being exposed directly to radiation fromsaid gases and heated preponderantly by radiation and so disposeddilferently, in relation to the gas flow, from said first-namedabsorptionstructure that it absorbs sufllcient heat materially to reducethe temperature of said gases for protection ci said firstheatabsorptionstructure, and means comprising a chamber for effecting atleast partial combustion before introduction of said gases into saidsecond-mentioned heating chamber.

25. Fluid heating apparatus for heating hydrocarbon iiuid to conversiontemperature comprising a combustion chamber, means for producing hotgases associated with said combustion chamber, a heating chamberreceiving hot gases formed in said combustion chamber. heat-absorptionstructure disposed in said heating chamber to receive heat by convectionfrom the gases, another heating chamber in communication with thedischarge end of the combustion chamber, heat-absorption structure insaid last-mentioned heating chamber horizontally disposed adjacent thedischarge end of the combustion chamber and substantially entirely belowsaid means for producing said hot gases and the discharge end of saidcombustion chamber and the point of withdrawal of said hot gases fromthe first-mentioned heating chamber, with substantially all of saidlast-mentioned heat-absorption structure being exposed directly toradiation from said gases and absorbing heat preponderantly byradiation, for limiting the temperature to which the rstnamedheat-absorption structure is subjected,

and-means connecting said absorption structures for passage of fiuidtherethrough in succession.

26. In a furnace comprising -a vertically arranged substantiallyycylindrical combustion chamber, a heating coil composed of a pluralityof vertically disposedv interconnected heat absorbing tubes adjacent tothe wall ofthe combustion chamber and disposed on an annular pitchcircle, the center of which substantially corresponds with the center ofthe combustion chamber, means for directing burning fuel and theproducts of combustion thereof in a central longitudinal andunobstructed path through said chamber and substantially out of contact'with said tubes, an insulated flue section free from heat absorbingtubes and leading from one end of said combustion chamber, asubstantially cylindrical outlet flue connected with said iiue section,and a plurality of tubes arranged longiconnected heat absorbing tubesadjacent to the wall of the combustion chamber and disposed on anannular pitch circle the center of which substantially corresponds withthe center of the combustion chamber, a burner located at one end of thechamber so positioned centrally with respect to said tubes as to impelits flame and the products of combustion in an unobstructed verticalpath substantially parallel to and out of direct contact with saidtubes, an insulated flue section free from heat absorbing tubes andleading from the end of said combustion chamber opposite to said burner,a horizontal outlet flue connecting with said flue section, and aplurality of tubes arranged longitudinally in the shape of a semi-circlein the lower part of saidA outlet iiue and forming a secondary heatabsorbing'unit.

28. In a furnace for heating oil, walls deilning a substantiallycylindrical heating chamber, a plurality of tubes arranged verticallyaround the inner periphery of said walls, means located in the uppercentral portion of said chamber` for producing and directing downwardlya high temperature radiant flame whereby radiant heat may be absorbed bysaid tubes, an lnsulated'ilue section free from heat absorbing tubesleading from the lower part of said chamber, a horizontal outlet iiuelconnecting with said flue section, and a plurality of tubes arrangedlongitudinally in the shape of a semi-circle in the lower part of saidoutlet iiue and adapted to be heated by said hot gases.- thereby forminga secondary radiant heat absorbing unit.

29. A furnace comprising a vertical heating section, a horizontalheating section, an economizer chamber, a plurality of interconnectedheat absorbing tubes in said heating sections and economizer chamber,means for-projecting a flame into said vertical section, means fordirecting the hotproducts of combustion through said horizontal sectionand through said economizer chamber, and separate insulated ue sectionsconnecting said vertical section and said horizontal section, and saidhorizontal section and said economizer chamber, respectively.

30. In a furnace comprising a vertically arranged substantiallycylindrical combustion chamber, a heating coil composed of a pluralityof vertically disposed interconnected heat absorbing tubes adjacent tothe wall of the combustion chamber and disposed on an annular pitchcircle, the center of which substantially corresponds with the center ofthe combustion chamber, means for directing burning fuel and theproducts of combustion thereof in a central longitudinal andunobstructed path through said chamber and substantially out of contactwith said tubes, an insulated flue section free from heat absorbingtubes and leading from the lower part of said combustion chamber, anoutlet flue connected wtih said flue section, and a plurality of heatingtubes all arranged longitudinally within said outlet flue and connectedto said iirst mentioned tubes, forming a secondary' heat absorbing unit.

3l. A furnace for heating oil, comprising walls forming a down draftradiant heating chamber, an insulated flue section free from heatabsorbing tubes and leading from the lower part of said heating chamber,an outlet flue connecting with said flue section and extendingsubstantially at right angles to said chamber, an economizer chamber, asecond insulated fiue section free from heat absorbing tubes connectingsaid economizer chamber and said outlet flue, means for directing aflame downwardly in said heating chamber, a

series of heat absorbing tubes in said heating the `velocity of theproducts of combustion passing through said economizer.

32. In a furnace, a heating chamber, heat-absorbing tubes therein, heatproducing means for heating said heat absorbing tubes by radiant heat,an insulated flue section leading from one end of said heating chamber,another heatingl chamber connected with said flue section, and aplurality of heat absorbing tubes connected to around thesurface of saidlast mentioned heating chamber and adapted to be heated by radiant andpartial convection heat.

33. In a furnace, a heating chamber, heat absorbing tubes therein, heatproducing means for heating said heat absorbing tubes by radiant heat,an insulated flue section leading from one end of said heating chamber,another heating chamber connected with 'said flue section, andsplurality of heat absorbing tubes connected to said first mentionedtubes disposed longitudinally around a portion of the surface of saidlast mentioned heating chamber and adapted to be heated by radiant andpartial convection heat.

34. In a furnace, a heating chambenheat absorbing tubes therein, heatproducing means for heating said heat absorbing tubes by radiant heat,`

' radiant and partial convection heat, and an economizer section havingheat absorbing tubes therein connected to said second mentioned heatingchamber,'the aforementioned heat absorbing tubes being connected to forma continuous path for a fluid to be heated.

' LUIS nl FLOREZ.

Ysaid first mentioned tubes disposed longitudinally

